Optical imaging systems typically comprise a detector, usually placed within a housing having an aperture through which the detector may view an external scene, and an optical subsystem that images the external scene onto the detector. For infrared imaging applications, the housing may be a cooling housing that maintains the detector at cryogenic temperatures to reduce thermal noise. The optical subsystem may be a telescope that projects a high quality image of predetermined magnification onto the detector. For many applications, the optical subsystem must be as compact as possible, while remaining consistent with required optical performance for high quality imaging.
Some systems that include optical imaging subsystems also include an optical illuminator for ranging or LADAR/LIDAR (Light Detection And Ranging; an optical remote sensing technology that is used to measure the distance to, or other properties of, a target by illuminating the target with light) purposes, for example. Some applications for these systems are such that separately packaging both the imaging subsystem and the illuminator does not pose a significant disadvantage or constraint. However, other applications have size and weight constraints that make it difficult or very disadvantageous to separately package both an aperture for the imaging subsystem and an aperture for the illuminator.